Dress will range from cargo shorts and Tshirt to slacks and polo or button down in most cases. Formal dress is no bigie as a dinner jacket easily covers my sig,
Caliber doesn't really matter but I don't want to go smaller than .380. I always have something in my vehicle so this will be a "gun to fight my way back to the gun I never should have left in the first place type"
As far as derringers a 357 in a gun that small is a bitch to hang onto.